The present invention relates to functional electrical stimulation (FES) of muscles to induce contraction thereof with electrical stimulus. More specifically, the present invention relates to electrically stimulating and exercising muscles to build muscle mass especially in patients having only partial or no nerve damage who might otherwise experience intolerable pain levels with such muscle stimulation.
Much work has been done in the area of functional electrical stimulation of muscles. Most notably, substantial success has been achieved in the area of building muscle mass of severely nerve damaged individuals such as paraplegics and/or quadriplegics by electrically stimulating the muscles sufficiently to induce work-producing contraction of the muscles ("power contraction").
The use of functional electrical stimulation for paralyzed individuals has been known to provide substantial health benefits in addition to building muscle mass. By way of example, U.S. Pat. No. 4,499,900, the disclosure of which is incorporated herein by reference, discloses an exercise bicycle which utilizes functional electrical stimulation to induce sufficient contraction of a paralyzed individual's leg muscles such that the individual's legs pedal an exercise bicycle through a complete and rigorous exercise routine thereby exercising otherwise atrophy-prone muscles. The exercise bicycle of that patent not only helps paraplegics and quadriplegics develop muscle mass, but improves their cardiovascular system, reduces and even eliminates pressure sores, and generally renders such individuals more physically fit with an improved prognosis for longevity. It would be desirable to provide such advantages to individuals having less nerve impairment than quadriplegics and paraplegics already aided by such a device.
In systems of the prior art adapted to provide power contraction of human muscle, the electrical therapeutic current stimulus coupled to the muscle typically has characteristics which, if applied to an individual without severe nerve damage associated with the muscles to be stimulated, could cause excruciating pain. Thus, individuals who are either not nerve-damaged or have only partial (but relevant) nerve-damage may not be able to take full advantage of functional electrical stimulation without risking severe pain. Thus, use of prior art "power contracting" type of systems have generally been limited to paraplegics and/or quadriplegics. However, many individuals, not just those suffering from severe nerve damage, could benefit from electrically-induced power contraction exercise therapy.